1. Technical Field
The present disclosure relates generally to batteries, and more specifically to management of battery cells within a rechargeable battery.
2. Description of Related Art
Battery management systems are commonly found in rechargeable batteries. Rechargeable batteries typically include one or more battery banks. The battery banks are also sometimes referred to as battery packs and are each made up of multiple rechargeable battery cells.
When using a rechargeable battery for a desired application, users often have three main concerns: protecting battery cells from damage, prolonging battery cell life, and maintaining battery cells in the state in which the battery cells were intended to be used in an application. Battery cell damage can result in danger to users, so safety may also be a concern when using rechargeable batteries.
One way to distinguish contemporary rechargeable batteries from older dry cell batteries is to compare the newer power cell batteries to the older energy cell batteries. Power cell batteries allow massive amounts of current to be provided with only a small amount of stored energy. Alternatively, dry cell batteries, such as an old truck battery, are able to supply a small amount of current for a long period of time because the dry cells hold a large amount of energy.
Contemporary rechargeable batteries are commonly replaced in one of two ways: first, on a schedule, possibly based on the rechargeable battery's expected life span; and second, subsequent the life of the rechargeable battery. Replacing a battery on a schedule and possibly prior to its expiration, or waiting until the death of a battery is often a costly approach.
To address this concern, a battery management system can monitor a number of parameters that affect performance of a rechargeable battery. The system can monitor the rechargeable battery cells of the rechargeable battery's battery pack. The system can monitor the battery cells and measure their state of charge (SOC), their state of health (SOH), and their internal and ambient battery temperatures.
Battery packs often operate with one of three battery cell technologies. These include Nickel-Cadmium (NiCd), Nickel-Metal Hydride (NiMH), and Lithium-Ion (Li-Ion). Each of these different battery cell technologies has their pros and cons. For example, on the one hand, Li-Ion battery cells have low weight and high energy, but are relatively expensive. On the other hand, NiCd and NiMH battery cells are less expensive for an equivalent weight, but will hold less energy than the Li-Ton battery cells.
A single Li-Ion battery cell within a standard battery pack typically provides an output voltage of around 3.7V. This output voltage commonly has a narrow range of safe operating voltages between 3V and 4.2V. Operation outside of this range can result in irreparable damage to the cells of a battery pack, which in turn can limit the life of the battery pack.